Segmental pulp wheel



Jan. 4, 938. G, E, RlCKARD 2,104,594

SEGMENTAL PULP WHEEL Filed June 18, 1957 2 sheets-sheet 1 l N VE NTOR.

GEORGE a. mcKARD' ATTORNEY.

Jan.. 4, 1938. Q B, RICKARD 2,104,594

SEGMENTL PULP WHEEL Filed June 18, 1957 A B'Sheets-Sheet 2 INVENTOR.

A TTORNEY.

GEORGE B. RICKARD Patented `an. 4, 19358 UNETED STATES ATNT QFFICE SEGMENTAL rpm WHEEL Application .lune 18, 1937, Serial No. 148,972

6 Claims.

This invention relates to the manufacture of pulp wheels and particularly to means for clamping segments of a pulp wheel more rmly when the wheel is subjected to heavier loads with consequent rise of temperature.

Many of the diiculties in maintaining segmental pulp wheels in good condition arise from large changes of temperature which tend to loosen the segments from their mountings. In northern latitudes the temperature of the outer parts of a pulp wheel in winter may range from 40 Fahrenheit when not in use to nearly the boiling-point oi water when the pulp wheel is being operated under heavy load. Clay-bonded abrasive segments containing silicon carbide or fused alumina abrasive grain, which have been bonded by heating the molded article to the temperature of vitriilcation, have coeicients of thermal expansion which are considerably less than those of the iron or steel drums on which they are usually mounted. The coefficients of eX- pansion of such vitrified segments may be only half that of their metal supports. It is therefore desirable, if possible, to mount the abrasive segments in such a manner that increase of load on the pulp wheel will not result in loosening of the clamps, but will tend to tighten the clamping means. One of the principal effects of increase of load is greatly increased friction between the periphery of the wheel and the logs which are pressed against it. The heat developed by this friction is conducted rapidly from the hot liquids which spread over the surface of the wheel to adjacent interior parts of the wheel and to metal connections.

One of the objects of the invention is to provide clamping means by which one or more abrasive segments can be clamped to a support by means accessible from the ends of the pulp wheel. Another object of the invention is to make the clamping means just referred to of such a character that there will be automatic compensation tending to resist loosening of the segments from the clamps and from the supporting base when the temperature of the pulp Wheel rises.

The improved mounting and clamping means for holding the abrasive segments against their support are illustrated by the accompanying drawings in which:

Figure l is a side View (perpendicular to the axis of rotation) of a'segmental pulp wheel that has been partly broken away to show the method of mounting the segments on their support and means for applying the necessary pull to firmly anchor thesegments to the support;

Figure 2 is a partial end View of the segmental pulp wheel shown in Figure 1 with a portion of the terminal covering broken away to give an end View of a toggle clamp;

Figure 3 is a partial end view oi a cast m-etal hub having inwardly extending pockets or housings in which the clamp control mechanism is to be inserted;

Figure 4 is a section on the line IV-IV of Figure 3;

Figure 5 is a side View of one of the screws used in regulating the pressure of a clamp against an abrasive segment;

Figure 6 is a side view of a pivot for a pair of toggle links, which pivot is threaded also for engagement with the regulating screw; and

Figure 7 is a side elevation of the segmental wheel mounted on a driving shaft.

Referring to the drawings in detail, abrasive segments 2 are shown in Figure 2 as mounted on a slotted metal hub 3 which has a periphery of general polygonal shape. The slots fl each communicate with thev interior of a pocket 5 which is used as a housing for part of the clamping mechanism and for the means which regulates the intensity of clamping. The inwardly projecting metal pockets 5 are embedded in the cement core 6. 'Ihe inwardly projecting pockets 5 and the peripheral portions l on which the abrasive segments rest are parts of one continuous casting which forms the hub 3. Each abrasive segment is formed with a T-shaped slot 8 into which a T-shaped clamping member 9 is inserted.

In the embodiment of the applicants pulp Wheel illustrated in Figure 1, the broken section shows two toggle clamping systems, each of which systems may be used to clamp one or more abrasive segments. Each toggle clamping system comprises a T-shaped clamping member 9 which fits into the T-shaped slot 8 in the base of its abrasive segment, a pair of clamping bars l l that are contained in the pocket 5 which communicates with the slot in the abrasive segment, outer links i2 which connect the T-shaped clamping member 9 with the toggle pivot I3, inner links i4 that connect the clamping bars Il with the toggle pivot I3, and a regulating screw l5 which is oppositely threaded at its opposite ends and which engages threaded holes in two oppositely disposed toggle pivots I3.

Each regulating screw l5 has a square end i6 which may be engaged by a wrench to push the pivot members i3 further apart or pull them closer together and hence tighten or loosen the clamping of the abrasive segment with respect to its metal support.

In order to minimize the effects of expansion of the links i2 and lli, theyy are made of a nickelsteel alloy having a very low coefficient of expansion. The clamping members 9 and Il can be made of structural steel having a coefficient of expansion that does not differ much from that of iron. The regulating screw I5 can be made, for example, of a bronze alloy which has a coeiiicient of expansion much greater than that of iron, such as phosphor bronze. Y Y

The purpose of this construction is to provide automatic temperature regulation of the clamping action. Increase of temperature of the assembly tends tol push the oppositely ,disposed pivots I3 further apart andV hence draw the abrasive segment toward its support, thus decreasing Ythe tendency of the segment to become looser as the'temperature of the pulp wheel rises. When the operation vof the pulp wheel ceases and the temperature ofthe wheel assembly falls, the rapid contraction of the regulating screw E5 tends to lighten the pressure of the clamps on the abrasive segment and hence lessens the danger of the building up of destructive pressures if the metal support should contract` more rapidly than the abrasive segments.

In the preparation of the wheel mounting,V the' pered sleeves i8. Each of these bushings has an external tapered surface which is complementary to the internal tapered surface of the sleeve I8 into which it fits, and each bushing has an internal cylindrical surface into which an assembly shaft (not shown) fits snugly. The wheel center (comprising principally the casting 3, the reinforced concrete core E, the sleeves l1 and I8, and the terminal bushings) is then mounted on the assembly shaft which in turn is mounted horizontally in bearings which permit turning the center by hand. The center is thus turned untilV one of the faces of the polygonal exterior surface of the casting 3 is brought into a horizontal upper position for mounting the first row of abrasive segments in position. These segmentsV (indicated at the top of Figure l) may be mounted one at a time or in groups of several segments which have been cemented together toY form a row of segments across the wheel face.

A thin layer of lead or other suitable yielding material is placed on the upper horizontal surface of the casting 3 as a packing material. A row of segments 2, as described in the paragraph next above, is then placed in position on the packing layer, six segments being indicated in the row at the top of Figure l.. cement or heat hardenable cement is used to join adjacent segments to each other. Where several segments are to be joind together by means of a heat hardenable cement, the surfaces to be joined are painted with the heat hardenable mix and the segments'brought together beforey assembly on the hub. A group of segments with joints of heat hardenable cement is heated to set A suitable cold setting the cement and is cooled before the group is placed on the hub member 3. The toggle clamps are then inserted into the pockets 5 and T-shaped slots 8. A thin packing of sheet lead is provided between the T-shaped clamping member 9 and the adjacent shoulders of the abrasive segment. In Figure 1 two toggle clamps are shown as holding three segments each on the supporting hub 3. The clamping pressure is adjusted from either end of the assembly by applying a wrench to the square ends' I 6 of the respective toggle control screws I5.

The hub is then turned until one of the adjacent exterior lat surfaces of the hub 3 is in a horizontal position. A resilient water-proof packing is provided between the two adjacent transverse rows of segments. Such a packing may be made, for example, from two sheets of fabric, which have been impregnated with a heat hardenable synthetic resin, a layer of vulcanizable rubber being inserted between the two impregnated sheets of fabric. intermediate layer are then heated to a temperature which will harden the synthetic resin and vuloanize the rubber. The cured compositel sheet built up in succession in a similar manner until the segmental abrasive rim is completed on the peripheral surface of the hub. The wheel is subsequently provided for operation with driving flanges as shown at 3| in Figure '7.

In Figure 1 each toggle control screw l5 is indicated as in'use for regulating the clamping pressure on three segments. A toggle control can, however, be provided for one or more segments in a row as thought desirable.

Y After the segments have been mounted firmly on their metal supports by adjustment of the toggle controls, the ends of each pocket 5 are closed by means of cover plates 25 as indicated in Figure 2, these plates being fastened by means of screws 26. The ends of the hub can be further sealed by means of cold-setting cement, fibrous packing or other suitable material.

If any particular segment of the completed wheel should be found to be defective, the nearest cover plate 25 can be removed and the toggle Y this joint material is structurally much weaker than the abrasive material of the defective segment, the necessary number of segments in the row that contains the defective segment can be removed with suitable tools. Y

The improved mounting for abrasive segments has a number of advantages from the point of view of ease of assembly and from the point of View of thev provision for quickly releasing the clamping pressure on one or more segments when it is necessary to replace them. One of the principal features is the automatic temperature control of clamping pressure on the segments. The abrasive segments can bemade by bonding, for example, silicon carbide or fused alumina grain with a clay bond, the molded segments being heated to the temperature of vitriflcation ofthe bond.

While many variations can be made in the ma.- terialsV of which the abrasive segments are made as well as in the materials used for joining the The sheets and thev segments and for making the toggle clamping system, theA invention is dened Within the compass of the following claims.

I claim:

1. In a segmental abrasive wheel means for clamping the abrasive segments to a rotatable support, said means comprising for each segment a clamping member in contact with one or more shoulders of said abrasive segment, a second clamping member in contact with one or more shoulders in a recess in the adjacent portion of the rotatable support, manually operable means for drawing said two clamping members toward each other to clamp the abrasive segment rrnly I to the rotatable support, and automatic means for pressing said clamping plates toward each other when the temperature of the wheel rises.

2. In a segmental abrasive Wheel means for clamping the segments to a metal support, said means comprising a pair of spaced toggle clamps adapted to Vary the pressure between a clamping plate and the base of an abrasive segment, and a screw which passes through the pivots of both toggle clamps in oppositely threaded engagement so that rotation of the screw in one direction v tightens the clamps and rotation in the opposite direction loosens the clamps.

3. In a segmental abrasive Wheel means for clamping abrasive segments to a metal hub, said means comprising a clamping member in concorresponding toggle group connecting the opposite ends of the segmental clamping member and the hub clamping member to a similar intermediate pivot member, and a screw which passes through both pivot members in oppositely threaded engagement so that rotation of the screw in one direction tightens the clamps and rotation in the opposite direction loosens the clamps.

4. The clamping means described in claim 3 in which the toggle arms are made of a metal having a low coeftlcient of expansion and in which the screw that connects the pivot members is made of a metal having a high coefficient of expansion so that rise of temperature of the wheel tends to bring the segmental clamping member closer to the hub clamping member.

5. The vclamping means described in claim 3 in which the toggle arms are made of nickel steel of the Invar type and in whichthe screw that connects the pivot members is made of phosphor bronze so that rise of temperature of the wheel tends to bring the segmental clamping plate closer to the hub clamping plate, thereby increasing the clamping pressure at operating temperature.

6. The abrasive wheel described in claim 1 in Which the hub is in the form of a metal casting having a slotted peripheral surface for supporting correspondingly slotted abrasive segments, clamping means extending from a recess in each abrasive segment through corresponding slots in the segment and hub to a toggle control housing extending inwardly from the peripheral surface of the casting and opening out from the slot therein, and a` cement core in intimate contact with the inner surface of the hub and holding the housing embedded therein.

GEORGE B. RICKARD. 

